Ralph,

With every new engine I have owned the required mixture settings for good running changed slightly during the break in process. Since I use only synthetics from the first run, the full process may take a smidge longer that "natural" oils. In any case, my mid ranges have always had a small "burbal" at those ranges until a few gallons had been run through and the final needle setttings had been obtained.

There's only one person that I personally know that has not had that "burbal" and he always leans the crap out of the enigne 'cuz he forgets which way to turn the needles.

Pat